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difference and any dust adhering to the neck of the flask washed
down with 5 c.c. pure cone, sulphuric acid and 30 c.c.
pure alcohol, which are slowly run in with shaking. A small
fragment of porous pot is also added. Twenty c.c. half-normal
alcoholic potash (see p. 210) are introduced into the round flask
(200 c.c.) which serves as receiver and 20 c.c. pure alcohol are
poured into the tap-funnel. The liquid in the flask is slowly distilled
whilst the alcohol is delivered drop by drop from the tap-funnel
at about the same rate as the liquid distils. The distillation is
continued until about half the bulk of liquid originally present
in the flask remains. This residue should be quite colourless.
The receiver is now attached to a reflux condenser and boiled
on the water-bath for -1, hour and finally titrated with half-normal
sulphuric acid, using' phenolphthalein as indicator.
The method does not give good results with acetamido-
compounds like acctaniliclc, &c.
K.vtiiiiplc.-.....0*663 gram naphthyl acetate required 7*5 c.c.
N/2 ROM.                "              '
?; x 0*04 3 x IOQ        f              .
  -          V          = 23-6 per cent.
2x0-633                [
Calculated for C,01!7.O.COCH, ; CjH.,0-23'1 per cent.
Tschttgaeff's Hydroxyl  Method.-........This method  rests
upon the action of hydroxyl compounds on magnesium methyl
iodide by which methane is evolved.
R.OII + Mg/^11-'5 - R.MgI + CH4.                                        fa
The apparatus   is an ordinary   Lunge nitrometer filled with                       \]   ,
mercury, which together with  the attached. Erlenmeyer flask                       5 ',
is  kept  at constant temperature by a flow of water through                        *^| i
an   outer jacket.    The  three-wav cock  is connected with the                       'if* I
*                                                                    '  '
Erlenmeyer flask (150 c.c.) by stout rubber tubing1.     A stock                        ff
solution   of magnesium   methyl   iodide   is   first  prepared   by                        V
mixing*   together   in  a   flask   connected   with   a   reflux  con-                        d
denser   100   grams    amyl   ether   distilled,   over   sodium,   9*6                       j,
grams clean magnesium ribbon and 35*5 grams dry methyl iodide                        Ij '
.and a few iodine crystals. After the first reaction is over the mix-                       \;(
ture is heated for i-2 hours on the water-bath with condenser to                        *>
expel unchanged methyl  iodide, and preserved in a vaselined                       '|  i
stoppered vessel.   About o'l0*15 gram /3-napUthol is accurately     .                   '^j